The present invention relates to device for non-contact or low-contact conveying of structural elements or materials along a conveying track. Furthermore, this invention relates to device for non-contact or low-contact handling and storing of structural elements and materials.
Several prior art technologies for moving or holding parts are known. For example, conveying systems utilizing magnetic repulsive forces or air cushions are widely used. Air cushions can be generated by air flowing through the nozzles which a plate is provided with. Another technology of generating air cushions is that of using sound waves.
A conveying device is described in the patent document U.S. Pat. No. 5,810,155, which is based on the principle of sound pressure. Further references concerning sound pressure and acoustic levitation are given in the literature as follows:
“Comparative contemplation on non-contact positioning of single droplets in aerodynamic, acoustic and electric force fields” by E. G. Lierke. Published in “Forschung im Ingenieurwesen”, vol. 61 (1995) 7/8, pages 201-216.
“Acoustic positioning—a comprehensive view on fundamentals and applications” by E. G. Lierke. Published in “Acustica” 82 (1996), pages 220-237.
The advice described in U.S. Pat. No. 5,810,155 comprises a conveying rail, to the front portion of which a vibration generator (source) is connected to excite this part so that a travelling wave is generated. The travelling wave initiated in this way extends along the conveying rail in conveying direction. The rear portion of this conveying rail is provided with a unit (drain) for converting the mechanic energy of the travelling wave into electric energy. This unit serves to prevent the travelling wave from being reflected and thereby, from moving back.
Objects positioned on the conveying rail are moved along it by the travelling air cushion generated between this rail and the bottom face of each of the objects in the direction to said unit. Results of trials show that it is possible to convey objects in this way, in principle.
Further structures of such prior art devices are described in the documents DE 19916922, DE 19916923, DE 19916856 and DE 19916872.
All of the known structures of near-field sound levitation are based on that a structural element is levitated and kept in this state in a non-contact way on a vibrating and, therefore, sound emitting surface. In order to gain such a state, it is required to cause this surface to vibrate. An expert in this field certainly knows that the oscillatory response of a solid body is mainly determined by the material and the dimensions thereof that is by its shape. For example, when a transporting track for transporting flat structural elements is to be constructed for a transport system, it has to be designed so that it is capable of vibrating and satisfies boundary conditions concerning the spatial requirements of such a transport system. However, it is difficult to design a device to be used for non-contact transporting, storing or handling of structural elements based on sound levitation, as it must have a predetermined geometric shape and predetermined dimensions to give it those vibration properties necessary for gaining levitation, but on the other hand, should have a totally different geometric shape with respect to the dimensions and weight in order to fulfil its task as a transport track, storing device, holding or handling device.
To elucidate this problem, it must be emphasized, that for example, a transport rail, on which an air cushion is generated by nozzles, is not subject to the limitation mentioned above, as there is the possibility to guide the air to the nozzles through channels which can randomly be configured and arranged. As flow effects inevitably occurring with certain technologies using gaseous media are not desired, such systems can not be installed everywhere.